1. Field of the Invention
The invention relates to a wireless communication system and particularly to a wireless communication system transferring audio data.
2. Description of the Background Art
In recent years, wireless communications that are performed between a plurality of information communication terminals without using an access point are becoming widely available. The network that is formed of only terminals capable of such wireless communications is called “ad hoc network”.
In the wireless communication system using the ad hoc network, the protocol is designed for the file transfer. Therefore, this kind of conventional wireless communication system is not suitable for data transfer such as audio stream reproduction that requires a real-time property in communications.
In the specification, the audio reproduction by the “streaming” is referred to as “audio stream reproduction”. The “streaming” indicates a technique which does not employ batch transfer such as conventional file transfer performed by downloading, but is configured to divide data on a sending side, to transfer continuously data items obtained by the division to a receiving side and, at the same time, to reproduce (i.e., output) continuously the data items received on the receiving side.
For example, Japanese Patent Laying-Open No. 2004-328692 has disclosed a conventional structure of a cordless speaker system. According to the publication of Japanese Patent Laying-Open No. 2004-328692, audio data is transferred by wireless communication between an audio amplifier and a speaker.
In the audio stream reproduction using the conventional wireless communication system, when the speaker system on the receiving side does not receive the audio data transmitted from the audio amplifier, such an operation may be performed that the speaker temporarily stops the audio output, and will output it after the speaker receives the audio data with a delay. In this case, a phenomenon such as interruption of the output sound or fluctuations in rhythm occurs to grate on listener's ears.
Although Japanese Patent Laying-Open No. 2004-328692 has disclosed the structure that allows a long-term use of a battery, it has not proposed any structure for avoiding the foregoing phenomenon that may occur when the speaker on the receiving side does not receive data.